20 replies to this topic

[pyrotechnist]

How do you go about making copper borate? I do not seem to get hardly any information about this chemical on the net. Does anyone know the safety of handling this chemical, how soluble it is, sensitivity and any other characteristics? I tried a msds search and nothing appeared.

[MDH]

I worked with it some time ago. It is easily prepared by the reaction of copper carbonate with boric acid in a warm solution. There are many varieties and it is easy to be confused - there are tetraborates and metaborates formed from commercial borax, but it seems like the grades you would want to use for color are formed by boric acid and copper carbonate, as the other ones contain much higher amounts of oxygen.

Many other nearly insoluble borates can be formed just by using a soluble barium, strontium or copper compound with borax, but they will of course be impure and need to be filtered for a long time.

So, "pesticide grade" boric acid, which you might also use to protect aluminum from being damaged, may be the best route.

I'm not sure what the properties of volatilized boron chloride are, but it should certainly lend a more greenish tinge based on just what I have read, balancing out the pink from potassium compounds.

The borate ion itself looks like it may be hard to simply decompose in a composition without the presence of sulfur and a strong chlorine donor.

[pyrotechnist]

could one not weed out the green spectrum of a copper borate based comp by fine tuning the heat produced? To what I have found on this virtually un-documented chemical when used to make a blue star it burns more of an aqua colour which surely means its burning more towards the green spectrum?

[MDH]

It could be - copper oxides also produce green, but I imagine that a small amount of HCB might cause it to be more green than a normal copper salt because it volatizes the boron at the same time as the copper. When I used copper borate, I combined it with shellac and ammonium perchlorate - and it burned very blue. But that was a long time ago, and I can't do tests with ammonium perchlorate anymore.

According to patents where it was used as a fire retardant, copper borate doesn't seem to decompose until a higher temperature is reached, like zinc borate, but in the presence of chlorine or a strong reducing agent, that process happens much more easily, which is why it was abandoned as a fire retardant in PVC.

And since the presence of chlorine is required to volatilize the ion, creating an apple green without the copper monochloride blue dominating it might be a challenge.

Perhaps sulfur could be used as a reducer instead.

[pyrotechnist]

Now then I wonder why a ordinery flame can get copper to emit the green though a firework cant I so hope to one day make a safer green unless I get my hands on amorphous boron :>. What other useful borates could I produce with boric acid or borax and any other chems? How hard is it to make barium borate pure?

[MDH]

Not hard. Simply react barium carbonate and boric acid in solutions. Perhaps certian borates could be used as delay agents - Though fuzzy I remember someone mentioning zinc borate being one for silver glitters, and also as a smoke additive.

[pyrotechnist]

I did try reacting Strontium Carbonate and boric acid but nothing seemed to happen accept I had a pile of strontium carbonate that just settled to the bottom.

[MDH]

That's bizarre. It should work. Instead, try reacting sodium carbonate with boric acid in a solution. Once all of the boric acid has dissolved, react that with a seperate solution of a soluble strontium salt, such as strontium acetate or citrate. Use a slight excess of boric acid after the sodium carbonate appears to have finished reacting to ensure that you don't end up with strontium carbonate.

[Mumbles]

I'm still not convinced that would work. I could not get boric acid to react with sodium bicarbonate in an acid/base manner. I'm a little surprised that you were able to react copper carbonate and boric acid. You are positive you have copper borate right, and not something else? Maybe heating was the key.

[MDH]

Yes, sodium carbonate will react with boric acid, though the reaction is slow. Heating the solutions will likely accelerate the reaction but mine were just warm. Adding water during the reaction will help. Since boric acid has a low solubility you will know when it has reacted entirely, it will no longer be in the solution.

Once that reaction is finished, add a slight excess of boric acid to ensure you don't obtain copper carbonate or hydroxide, then add copper sulfate.

The result will be a dark green or blue powder which turns to an azure or sky-blue, rich looking powder when it is fine.

I wouldn't stop at borate... I'm looking into chlorostannates... but I will leave you at borate for now since it has already been tested.

[pyrotechnist]

I managed to get copper borate from borax in hot water and copper sulphate which instantly made a light blue thick participate which I then drained and now have nice dried blue chunks lol, is this correct? Now my copper carbonate and boric acid one seems to just be forming white crystals and contains a dark green mass at the bottom, which one is the borate and how do I filter it out?

[MDH]

The problem is, that is copper either copper tetraborate. The form used for colors is produced by the above reaction.

I don't doubt that copper tetraborate has some uses - perhaps it could be tried as a delay agent. But there are much less exotic ways to do that.

[pyrotechnist]

Once I get some more perc again I will try it out, it does make good flash powder though! Do you know how dangerous the tetraborate version is to handle? Btw what would be the copper borate within my second boric acid + copper carb solution, one section has a dark green powder at the bottom and then I have some white crystals that are forming on the sides and on top of the solution.

[MDH]

I would assume that if you did it properly that is copper borate, and the crystals are boric acid from a slight excess. Did you react sodium bicarbonate with boric acid then add copper sulfate, or just mix copper carbonate and boric acid together? I made a slight mistake in an earlier post saying that borates are produced by the straight reaction of carbonates and boric acid. Since borates are (mostly) nearly insoluble you will need to use at least one highly soluble salt. There are many options, though I prefer either the sulfate or acetate route.

What did you make a flash powder from copper tetraborate out of?

[pyrotechnist]

I just mixed boric acid and copper carbonate together in boiling hot water, So do I need to dissolve sodium bicarb and then add boric acid and then a copper sulphate solution to create copper borate? I assume you then filter it out and discard of the liquid that is left?

I used 300# mesh MgAL, hard to light but makes a good thump.